1. Field of the Invention
The present invention relates to a control apparatus for a vehicle, and more particularly to a control apparatus for a vehicle mounted with an internal combustion engine having a first fuel injection mechanism (in-cylinder injector) for injecting fuel into a cylinder and a second fuel injection mechanism (intake manifold injector) for injecting fuel into an intake manifold and/or an intake port.
2. Description of the Background Art
A fuel injection apparatus provided with an in-cylinder injector for injecting fuel into a cylinder and an intake manifold injector for injecting fuel into an intake port, and controlling the in-cylinder injector and the intake manifold injector in accordance with an operation state to inject the fuel by combination of intake manifold injection and in-cylinder direct injection is known (e.g., Japanese Patent Laying-Open No. 07-103048, which is also referred to as “Patent Document 1” hereinafter).
In a fuel supply system for supplying the fuel at a prescribed fuel pressure to the injectors, generally, one fuel line extending from a fuel tank toward the internal combustion engine is branched in the vicinity of the internal combustion engine so as to supply the fuel to the intake manifold injector and to the in-cylinder injector. With this configuration, however, the fuel line has a complicated configuration in the vicinity of the internal combustion engine, and the fuel supplied from the fuel tank may be subjected to a great amount of heat from the engine block of the internal combustion engine. The fuel supplied to the intake manifold injector is a fuel of a low pressure that is pumped up from the fuel tank by using a low-pressure fuel pump. As such, it has been pointed out that the fuel, when subjected to the great amount of heat from the engine block, may partially vaporize in the fuel line or a delivery pipe for supplying the fuel into the intake manifold injector, leading to occurrence of vapor lock.
To address such a problem, for example, Japanese Patent Laying-Open No. 2004-278347 (hereinafter, also referred to as “Patent Document 2”) discloses a fuel supply system in which a fuel tank, a low-pressure fuel pump, a fuel pressure regulator (pressure regulator), an intake manifold injection (low-pressure) delivery pipe, a high-pressure fuel pump, an in-cylinder injection (high-pressure) delivery pipe, and a relief valve are arranged in series. In a fuel injection apparatus provided with such a fuel supply system, it is possible to prevent fuel injection failure attributable to the vapor lock caused in the pipe connected to the intake manifold injector, with a simple configuration.
In the fuel injection apparatus disclosed in Patent Document 2, the intake manifold injection (low-pressure) delivery pipe is arranged downstream of the fuel pressure regulator. Thus, although an electromagnetic relief valve for releasing pressure is arranged downstream of the in-cylinder injection (high-pressure) delivery pipe, it is difficult to intentionally release the fuel pressure of the low-pressure delivery pipe at the time of stop of operation of the vehicle. This leads to poor oil tightness, and there may occur leakage of the fuel from the intake manifold fuel injection valve during stop of operation of the vehicle. Such leakage of the fuel may lead to deterioration in emission performance at the time of next start of the engine.
In a hybrid vehicle further provided with an electric motor as another source of driving force other than the internal combustion engine, or in a vehicle mounted with a so-called economy running system that forcibly stops idling of the engine at the time of temporary stop of the vehicle (hereinafter, also simply called the “eco run vehicle”), “engine intermittent operation control” is carried out in which an engine is temporarily stopped when a prescribed engine stop condition is satisfied, and restarted in response to fulfillment of an engine stop reset condition.
In the vehicle conducting such engine intermittent operation control, there are two cases of engine stop: one is stop associated with end of vehicle operation, and the other is temporary stop with an assumption of restart of the engine. While it is necessary to secure quick starting capability upon restart of the engine in the case of temporary stop of the engine according to the engine intermittent operation control, at the time of engine stop associated with the end of vehicle operation, it is necessary to prevent deterioration in emission performance upon next start of vehicle operation attributable to degradation in oil tightness.
Further, there are also two cases of engine start: one is initial start associated with start of vehicle operation, and the other is restart following temporary stop in the engine intermittent operation. It is preferable to set optimal engine starting conditions for the respective cases for the purposes of securing starting capability of the engine as well as preventing deterioration in emission performance.